Cloud computing is known as a type of services allowing users to utilize computing resources available on a network of servers, as needed, with their terminal devices and network connections. The available computer resources include, for example, data processing functions that are realized by executing application programs on a computer. Such data processing functions are referred to herein as “applications”. A variety of applications are provided by many servers on the Internet. The users make access to different servers from their terminal devices, depending on what application services to use to achieve their respective purposes.
In relation to the provision of services to users, the servers may be configured to hold personal data of the users, so as to allow an application to use such data during its execution. One of the benefits of letting servers manage users' personal data is that the users can receive personalized services wherever they are. The personal data of users may include, for example, documents that they edited, attribute data (e.g., name and residence address) of individuals, and information about the environment in which they use applications (e.g., mail server name, mail address, password).
The servers on the network manage such personal data of users, and various useful techniques may be applied for this purpose. For example, one proposed system is designed to deliver data files to a requesting client terminal in encrypted form by using a cryptographic key associated with that client terminal. In this system, the client terminal can decode encrypted data files with a decryption key only if the client terminal is authenticated as the rightful destination of the files. Another proposed technique permits an application system to use a plurality of different databases in a unified manner.
Japanese Laid-open Patent Publication No. 2006-99491
Japanese Laid-open Patent Publication No. 2006-302159
Some users may use a plurality of applications provided in different servers. This means, however, that their personal data is distributed across a plurality of servers. The users are more burdened with the management of their personal data in those servers.